Combination oil ring

ABSTRACT

A combination oil ring includes a pair of upper and lower side rails and a spacer expander arranged there between, the spacer expander including a plurality of upper pieces and lower pieces alternately arranged in a circumferential direction with the pieces axially and circumferentially apart from each other, a coupling piece coupling pieces adjacent to each other, and flange portions formed standing at inner circumferential-side end portions of the upper pieces and the lower pieces so as to press the side rails, and a through hole being formed in the flange portions, wherein side rail support portions that project axially are formed at portions in the circumferential direction of outer circumferential-side end portions of the upper pieces and the lower pieces.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. PatentApplication Ser. No. 14/349,821, filed on Apr. 4, 2014, the entirecontents of which are incorporated herein by reference and priority towhich is hereby claimed. Application Ser. No. 14/349,821 is the U.S.National stage of application No. PCT/JP2012/070074, filed on Aug. 7,2012. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimedfrom Japanese Application No. 2011-247286, filed Nov. 11, 2011, andJapanese Application No. 2011-279642, filed Dec. 21, 2011, and JapaneseApplication No. 2012-029097, filed Feb. 14, 2012, the disclosures ofwhich are also incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a three-piece combination oil ring.

BACKGROUND ART

When a three-piece combination oil ring including a pair of upper andlower side rails and a spacer expander arranged therebetween is used,sludge such as unburned carbon or carbon produced from a product ofcombustion of lubricant oil tends to be deposited between the spacerexpander and the side rails. With a progression of deposition, the siderails and the spacer expander stick to each other due to deposits, andthe side rails cannot follow the shape of a cylinder bore, so that theoil ring may not be able to exert predetermined performance as an oilring.

Meanwhile, in Patent Literature 1, a hole large enough to cause sludgeto pass therethrough is formed in a center portion between convex andconcave portions of an expander each having a substantially flatsurface.

Also, in Patent Literature 2, a groove is formed in a surface that isclose to a side rail of an upper piece and a surface that is close to aside rail of a lower piece of a spacer expander, and the groovecommunicates with a through hole formed in a flange portion for pressingthe side rails in a combination oil ring. Also, since the groove extendsradially and is open on an outer circumferential side, oil flows in fromthe opening portion to form a flow of oil from the outer circumferentialside to an inner circumferential side, so that the oil containing sludgeis easily discharged from the through hole in the flange portion,thereby making it difficult for deposits to accumulate.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Utility Model Publication No. 2-31559

Patent Literature 2: Japanese Patent Laid-Open No. 2011-185383

SUMMARY OF INVENTION Technical Problem

In Patent Literature 1, however, since the hole is formed in the centerportion between the convex and concave portions each having asubstantially flat surface of the expander, the expander may lackrigidity.

Also, although Patent Literature 2 further proposes the technique forpreventing the side rails and the spacer expander of the combination oilring from sticking to each other, there is a demand for a furtherimprovement in the performance of discharging the oil containing sludge.

It is an object of the present invention to prevent side rails and aspacer expander of a combination oil ring from sticking to each other.

Solution to Problem

The present invention is a combination oil ring including a pair ofupper and lower side rails and a spacer expander arranged therebetween,the spacer expander including a plurality of upper pieces and lowerpieces alternately arranged in a circumferential direction with thepieces axially and circumferentially apart from each other, a couplingpiece coupling an upper piece and a lower piece adjacent to each other,and a flange portion formed standing at an inner circumferential-sideend portion of each of the upper pieces and the lower pieces so as topress the side rails, and a through hole being formed in the flangeportion,

-   -   wherein a side rail support portion that projects axially is        formed at a portion in the circumferential direction of an outer        circumferential-side end portion of each of the upper pieces and        the lower pieces of the spacer expander.

The side rail support portion of the spacer expander may preferably beformed at an end portion in the circumferential direction of the outercircumferential-side end portion of each of the upper pieces and thelower pieces, or at a portion including the end portion.

The side rail support portion of the spacer expander may preferably beformed at a position of an intermediate portion in the circumferentialdirection of the outer circumferential-side end portion of each of theupper pieces and the lower pieces.

A portion other than the side rail support portion in thecircumferential direction of the outer circumferential-side end portionof each of the upper pieces and the lower pieces of the spacer expandermay preferably have a flush surface continuous from an innercircumferential side.

A portion other than the side rail support portion in thecircumferential direction of the outer circumferential-side end portionof each of the upper pieces and the lower pieces of the spacer expandermay preferably project to an axially opposite side from the side railsupport portion. In this case, the portion other than the side railsupport portion in the circumferential direction of the outercircumferential-side end portion of each of the upper pieces and thelower pieces of the spacer expander may preferably have a radial throughhole on an inner circumferential side.

Each of gaps between the upper and lower pieces of the spacer expanderand the side rails may preferably be continuously or discontinuouslywidened radially inward from an inner circumferential side of the siderail support portion to a base portion of the flange portion.

Preferably, a groove may be formed in a surface that is close to theside rail of at least the upper piece out of the upper and lower piecesof the spacer expander, and the groove may communicate with the throughhole in the flange portion. Preferably, in this case, the groove mayextend radially, and may be open on an outer circumferential side.

The side rail support portion of the spacer expander is formed in atrapezoidal shape, a semi-elliptical shape, or a rectangular shape asviewed from the radial direction.

Although a side rail support surface of the side rail support portion ofthe spacer expander may be a flat surface, the present invention is notlimited thereto, and, for example, the side rail support surface maypreferably be radially formed as a tapered surface or an arc surface soas to support the side rails at the outer circumferential-side endportion.

The side rail support portion of the spacer expander may preferably beformed by plasticity processing.

Advantageous Effects of Invention

In accordance with the present invention, since the side rail supportportion is formed at a portion in the circumferential direction of theouter circumferential-side end portion of the spacer expander, a spaceis formed between the spacer expander and the side rails at the portionother than the side rail support portion in the circumferentialdirection of the outer circumferential-side end portion of the spacerexpander. As a result, oil flows in from the space to form a flow of oilfrom the outer circumferential side to the inner circumferential side,and the oil containing sludge is easily discharged from the through holein the flange portion of the spacer expander, so that the side rails andthe spacer expander can be prevented from sticking to each other due todeposits.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to one embodiment of the present invention.

FIG. 2 is a perspective view illustrating a portion of a spacerexpander.

FIG. 3 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to another embodiment of the present invention.

FIG. 4 is a perspective view illustrating a portion of a spacerexpander.

FIG. 5 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to yet another embodiment of the present invention.

FIG. 6 is a perspective view illustrating a portion of a spacerexpander.

FIG. 7 is a perspective view illustrating a portion of yet anotherspacer expander of the present invention.

FIG. 8 is a perspective view illustrating a portion of yet anotherspacer expander of the present invention.

FIG. 9 is a perspective view illustrating a portion of yet anotherspacer expander of the present invention.

FIG. 10 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to yet another embodiment of the present invention.

FIG. 11 is a perspective view illustrating a portion of a spacerexpander.

FIG. 12 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to yet another embodiment of the present invention.

FIG. 13 is a perspective view illustrating a portion of a spacerexpander.

FIG. 14 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to yet another embodiment of the present invention.

FIG. 15 is a perspective view illustrating a portion of a spacerexpander.

FIG. 16 is a vertical sectional view illustrating a state in which apiston to which a combination oil ring is mounted is inserted into acylinder according to yet another embodiment of the present invention.

FIG. 17 is a perspective view illustrating a portion of a spacerexpander.

FIG. 18 is a perspective view illustrating a portion of yet anotherspacer expander of the present invention.

FIG. 19 is a perspective view illustrating a portion of yet anotherspacer expander of the present invention.

FIG. 20 is a view of a side rail support portion as viewed from a radialdirection.

FIG. 21 is a view of a side rail support portion as viewed from a radialdirection.

FIG. 22 is a vertical sectional view illustrating a portion of acombination oil ring.

FIG. 23 is a vertical sectional view illustrating a portion of acombination oil ring.

FIG. 24 is a view for explaining a dimensional relationship of a siderail support portion.

FIG. 25 is a view for explaining a dimensional relationship of a siderail support portion.

FIG. 26 is a view illustrating an axial distance c between a flangeportion base position of a spacer expander and a side rail, and an axialwidth d of an outer circumferential-side end portion of the spacerexpander.

DESCRIPTION OF EMBODIMENTS

In the following, one embodiment of the present invention will bedescribed based on FIGS. 1 and 2.

In FIG. 1, a combination oil ring 10 is mounted to an oil ring groove 4formed in an outer circumferential surface 3 of a piston 2 within acylinder 1. The combination oil ring 10 is a three-piece combination oilring made of steel, and includes a pair of upper and lower side rails 11and 12, and a spacer expander 13 arranged therebetween.

The side rails 11 and 12 are annular plate-like rails each provided witha gap.

The spacer expander 13 (see FIGS. 1 and 2) is composed of a plurality ofaxially-corrugated periodic elements lying in series in acircumferential direction. In the spacer expander 13, a plurality ofhorizontal upper and lower pieces 14 and 15 are alternately arranged inthe circumferential direction with the pieces axially andcircumferentially apart from each other, and an upper piece 14 and alower piece 15 adjacent to each other are coupled together with acoupling piece 16. Flange portions 17 and 18 for pressing the side rails11 and 12 are formed standing in an arched shape at innercircumferential-side end portions of each of the upper pieces 14 andeach of the lower pieces 15, and a through hole 19 is formed in each ofbase portions of the flange portions 17 and 18.

In outer circumferential-side end portions of each of the upper pieces14 and each of the lower pieces 15, end portions in the circumferentialdirection project axially outward to form support portions 14 a and 15 afor the side rails 11 and 12. That is, one end portion in thecircumferential direction of the outer circumferential-side end portionof the upper piece 14 projects upward to form the support portion 14 afor the side rail 11, and one end portion in the circumferentialdirection of the outer circumferential-side end portion of the lowerpiece 15 projects downward to form the support portion 15 a for the siderail 12. Portions 14 b and 15 b other than the side rail supportportions in the circumferential direction of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 have horizontal surfaces continuous from the innercircumferential side.

Accordingly, in the upper piece 14 and the lower piece 15, the endportions in the circumferential direction of the outercircumferential-side end portions project axially to constituteprojecting surfaces that form the side rail support portions 14 a and 15a, and the other portions (the portions other than the side rail supportportions) 14 b and 15 b constitute the horizontal surfaces continuousfrom the inner circumferential side.

The spacer expander 13 is mounted in the oil ring groove 4 of the piston2 in a compressed state with both gap end portions abutted against eachother so as to generate a radially-outward expansion force, and bringsan outer circumferential surface of each of the side rails 11 and 12into close contact with an inner wall of the cylinder 1 by holding theupper and lower side rails 11 and 12 vertically (axially) apart fromeach other by the side rail support portions 14 a and 15 a of the upperand lower pieces 14 and 15, and pressing inner circumferential surfacesof the upper and lower side rails 11 and 12 by the upper and lowerflange portions 17 and 18, respectively. Accordingly, the outercircumferential surfaces of the upper and lower side rails 11 and 12come into press contact with the inner wall of the cylinder 1, andthereby scrape oil off the inner wall of the cylinder 1.

As described above, in the combination oil ring 10 according to thepresent embodiment, the side rail support portions 14 a and 15 a of thespacer expander 13 are formed at the end portions in the circumferentialdirection of the outer circumferential-side end portions of the upperpiece 14 and the lower piece 15, so that spaces are formed between theupper piece 14 of the spacer expander 13 and the upper side rail 11, andbetween the lower piece 15 of the spacer expander 13 and the lower siderail 12, at the portions 14 b and 15 b other than the side rail supportportions in the circumferential direction of the outercircumferential-side end portions. As a result, oil flows in from thespaces to form a flow of oil from the outer circumferential side to theinner circumferential side, and the oil containing sludge is easilydischarged from the respective through holes 19 in the flange portions17 and 18 of the spacer expander 13, so that the side rails 11 and 12and the spacer expander 13 can be prevented from sticking to each otherdue to deposits.

FIGS. 3 and 4 show another embodiment of the present invention. Thecombination oil ring 10 according to the present embodiment differs fromthe combination oil ring according to the aforementioned embodiment inthe configuration of the portions 14 b and 15 b other than the side railsupport portions in the circumferential direction of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 of the spacer expander 13 as described below, and the otherconfigurations are the same as those in the aforementioned embodiment.

In the present embodiment, in the outer circumferential-side endportions of the upper piece 14 and the lower piece 15 of the spacerexpander 13, the end portions in the circumferential direction alsoproject axially outward to form the support portions 14 a and 15 a forthe side rails 11 and 12. That is, the end portion in thecircumferential direction of the outer circumferential-side end portionof the upper piece 14 of the spacer expander 13 projects upward to formthe support portion 14 a for the side rail 11, and the end portion inthe circumferential direction of the outer circumferential-side endportion of the lower piece 15 projects downward to form the supportportion 15 a for the side rail 12.

However, in the present embodiment, the portions 14 b and 15 b otherthan the side rail support portions in the circumferential direction ofthe outer circumferential-side end portions of the upper piece 14 andthe lower piece 15 of the spacer expander 13 are configured as follows.That is, the portions 14 b and 15 b other than the side rail supportportions in the circumferential direction of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 project to axially opposite sides from the side rail supportportions 14 a and 15 a, and a radial through hole 20 is formed in eachof the inner circumferential sides. That is, the portion 14 b other thanthe side rail support portion in the circumferential direction of theouter circumferential-side end portion of the upper piece 14 of thespacer expander 13 projects downward to be formed one-step lower thanthe horizontal surface portion on the inner circumferential side, withthe radial through hole 20 formed on the inner circumferential side, andthe portion 15 b other than the side rail support portion in thecircumferential direction of the outer circumferential-side end portionof the lower piece 15 projects upward to be formed one-step higher thanthe horizontal surface portion on the inner circumferential side, withthe radial through hole formed on the inner circumferential side.

As described above, in the combination oil ring 10 according to thepresent embodiment, the side rail support portions 14 a and 15 a of thespacer expander 13 are formed at the end portions in the circumferentialdirection of the outer circumferential-side end portions of the upperpiece 14 and the lower piece 15, so that spaces are formed between theupper piece 14 of the spacer expander 13 and the upper side rail 11, andbetween the lower piece 15 of the spacer expander 13 and the lower siderail 12, at the portions 14 b and 15 b other than the side rail supportportions in the circumferential direction of the outercircumferential-side end portions. As a result, oil flows in from thespaces to form a flow of oil from the outer circumferential side to theinner circumferential side, and the oil containing sludge is easilydischarged from the respective through holes 19 in the flange portions17 and 18 of the spacer expander 13, so that the side rails 11 and 12and the spacer expander 13 can be prevented from sticking to each otherdue to deposits. Moreover, in the present embodiment, the portions 14 band 15 b other than the side rail support portions project to theaxially opposite sides from the side rail support portions 14 a and 15a, and the radial through hole 20 is formed in each of the innercircumferential sides, so that the oil passes through the portions 14 band 15 b other than the side rail support portions to be discharged tothe inner circumferential side from the radial through holes 20, therebymaking it difficult for the sludge to accumulate between the spacerexpander 13 and the side rails 11 and 12.

FIGS. 5 and 6 show yet another embodiment of the present invention. Thecombination oil ring 10 according to the present embodiment differs fromthe combination oil ring according to the first embodiment describedusing FIGS. 1 and 2 in the configuration of portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13as described below, and the other configurations are the same as thosein the first embodiment.

In the present embodiment, in the outer circumferential-side endportions of the upper piece 14 and the lower piece 15 of the spacerexpander 13, the end portions in the circumferential direction alsoproject axially outward to form the support portions 14 a and 15 a forthe side rails 11 and 12. That is, the end portion in thecircumferential direction of the outer circumferential-side end portionof the upper piece 14 of the spacer expander 13 projects upward to formthe support portion 14 a for the side rail 11, and the end portion inthe circumferential direction of the outer circumferential-side endportion of the lower piece 15 projects downward to form the supportportion 15 a for the side rail 12.

However, in the present embodiment, the portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13are configured as follows. That is, a groove 21 that extends linearly inthe radial direction is formed in the portion on the innercircumferential side from the side rail support portion in each of asurface that is close to the side rail 11 of the upper piece 14 and asurface that is close to the side rail 12 of the lower piece 15 of thespacer expander 13. The grooves 21 are formed by deforming predeterminedportions of the upper piece 14 and the lower piece 15 into an arc shapein section by plasticity processing. Inner circumferential-side endportions of the grooves 21 in the upper piece 14 and the lower piece 15communicate with the through holes 19 in the base portions of the flangeportions 17 and 18, respectively, and outer circumferential-side endportions are open to an external space so as to communicate with theexternal space. Reference numeral 22 denotes the opening. Although thesectional shape of the groove 21 is shown as an arc shape, the presentinvention is not limited thereto, and, for example, an invertedtrapezoidal shape or a V shape may be also used.

As described above, in the combination oil ring 10 according to thepresent embodiment, the side rail support portions 14 a and 15 a of thespacer expander 13 are formed at the end portions in the circumferentialdirection of the outer circumferential-side end portions of the upperpiece 14 and the lower piece 15, so that spaces are formed between theupper piece 14 of the spacer expander 13 and the upper side rail 11, andbetween the lower piece 15 of the spacer expander 13 and the lower siderail 12, at the portions 14 b and 15 b other than the side rail supportportions in the circumferential direction of the outercircumferential-side end portions. As a result, oil flows in from thespaces to form a flow of oil from the outer circumferential side to theinner circumferential side, and the oil containing sludge is easilydischarged from the respective through holes 19 in the flange portions17 and 18 of the spacer expander 13, so that the side rails 11 and 12and the spacer expander 13 can be prevented from sticking to each otherdue to deposits. Moreover, in the present embodiment, the grooves 21 areformed in the upper piece 14 and the lower piece 15 of the spacerexpander 13, so that the sizes of the through holes 19 provided at thebase portions of the flange portions 17 and 18 and facing the spaceportions between the side rails 11 and 12 and the spacer expander 13 canbe formed larger by sizes corresponding to the grooves 21 than those ofthe flat surfaces with no groove; therefore, the deposits between theupper and lower pieces 14 and 15 of the spacer expander 13 and the siderails 11 and 12 are easily discharged from the through holes 19 in theflange portions 17 and 18 of the spacer expander 13, and the side rails11 and 12 and the spacer expander 13 can be prevented from sticking toeach other due to the deposits. Also, since the grooves 21 extend in theradial direction and are open to the external space so as to communicatewith the external space without being closed on the outercircumferential side, the oil flows in from the openings 22 to form aflow of oil from the outer circumferential side to the innercircumferential side; therefore, the deposits become difficult toaccumulate and easily discharged from the through holes 19 in the flangeportions 17 and 18, so that the side rails 11 and 12 and the spacerexpander 13 can be further prevented from sticking to each other due tothe deposits.

The structure of the grooves 21 described in the aforementionedembodiment may be also applied to the combination oil ring according tothe embodiment described using FIGS. 3 and 4.

Also, although the side rail support portions 14 a and 15 a formed atthe end portions in the circumferential direction of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 of the spacer expander 13 are formed at the end portionscircumferentially opposite to each other of the outercircumferential-side end portions in the aforementioned embodiments, theside rail support portions 14 a and 15 a may be, of course, formed onthe same side. Accordingly, the rigidity of the spacer expander 13 isincreased.

The above example is shown in FIGS. 7 to 9.

FIG. 7 corresponds to the first embodiment shown in FIGS. 1 and 2, inwhich the side rail support portions 14 a and 15 a of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 of the spacer expander 13 are formed at the end portions on thesame side in the circumferential direction. The other configurations arethe same as those in the first embodiment shown in FIGS. 1 and 2. In thepresent embodiment, the same effects as those in the embodiment shown inFIGS. 1 and 2 are produced, and the rigidity of the spacer expander 13can be also improved.

FIG. 8 corresponds to the embodiment shown in FIGS. 3 and 4, in whichthe side rail support portions 14 a and 15 a of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 of the spacer expander 13 are formed at the end portions on thesame side in the circumferential direction. The other configurations arethe same as those in the embodiment shown in FIGS. 3 and 4. In thepresent embodiment, the same effects as those in the embodiment shown inFIGS. 3 and 4 are produced, and the rigidity of the spacer expander 13can be also improved.

FIG. 9 corresponds to the embodiment shown in FIGS. 5 and 6, in whichthe side rail support portions 14 a and 15 a of the outercircumferential-side end portions of the upper piece 14 and the lowerpiece 15 of the spacer expander 13 are formed at the end portions on thesame side in the circumferential direction. The other configurations arethe same as those in the embodiment shown in FIGS. 5 and 6. In thepresent embodiment, the same effects as those in the embodiment shown inFIGS. 5 and 6 are produced, and the rigidity of the spacer expander 13can be also improved.

FIGS. 10 and 11 show yet another embodiment of the present invention.The combination oil ring 10 according to the present embodiment differsfrom the combination oil ring according to the first embodimentdescribed using FIGS. 1 and 2 in the configuration of the side railsupport portions 14 a and 15 a of the outer circumferential-side endportions of the upper piece 14 and the lower piece 15 of the spacerexpander 13 as described below, and the other configurations are thesame as those in the first embodiment.

In the present embodiment, in the outer circumferential-side endportions of the upper piece 14 and the lower piece 15 of the spacerexpander 13, center portions in the circumferential direction projectaxially outward to form support portions 14 a and 15 a for the siderails 11 and 12. That is, the center portion in the circumferentialdirection of the outer circumferential-side end portion of the upperpiece 14 projects upward to form the support portion 14 a for the siderail 11, and the center portion in the circumferential direction of theouter circumferential-side end portion of the lower piece 15 projectsdownward to form the support portion 15 a for the side rail 12. Portions14 b and 15 b other than the side rail support portions in thecircumferential direction of the outer circumferential-side end portionsof the upper piece 14 and the lower piece 15, that is, both sideportions 14 b and 15 b of the side rail support portions 14 a and 15 ahave horizontal surfaces continuous from the inner circumferential side.

Accordingly, in the upper piece 14 and the lower piece 15 of the spacerexpander 13, the center portions in the circumferential direction of theouter circumferential-side end portions project axially to constituteprojecting surfaces that form the side rail support portions 14 a and 15a, and the other portions (the portions other than the side rail supportportions) 14 b and 15 b constitute the horizontal surfaces continuousfrom the inner circumferential side.

As described above, in the combination oil ring 10 according to thepresent embodiment, the side rail support portions 14 a and 15 a of thespacer expander 13 are formed at the center portions in thecircumferential direction of the outer circumferential-side end portionsof the upper piece 14 and the lower piece 15, so that spaces are formedbetween the upper piece 14 of the spacer expander 13 and the upper siderail 11, and between the lower piece 15 of the spacer expander 13 andthe lower side rail 12, at the both side portions 14 b and 15 b of theside rail support portions 14 a and 15 a in the circumferentialdirection of the outer circumferential-side end portions. As a result,oil flows in from the spaces to form a flow of oil from the outercircumferential side to the inner circumferential side, and the oilcontaining sludge is easily discharged from the respective through holes19 in the flange portions 17 and 18 of the spacer expander 13, so thatthe side rails 11 and 12 and the spacer expander 13 can be preventedfrom sticking to each other due to deposits.

FIGS. 12 and 13 show yet another embodiment of the present invention.The combination oil ring 10 according to the present embodiment differsfrom the combination oil ring according to the aforementioned embodimentdescribed using FIGS. 10 and 11 in the configuration of portions on theinner circumferential side from the side rail support portions 14 a and15 a of the upper piece 14 and the lower piece 15 of the spacer expander13 as described below, and the other configurations are the same asthose in the aforementioned embodiment.

In the present embodiment, in the outer circumferential-side endportions of the upper piece 14 and the lower piece 15 of the spacerexpander 13, the center portions in the circumferential direction alsoproject axially outward to form the support portions 14 a and 15 a forthe side rails 11 and 12. That is, the center portion in thecircumferential direction of the outer circumferential-side end portionof the upper piece 14 of the spacer expander 13 projects upward to formthe support portion 14 a for the side rail 11, and the center portion inthe circumferential direction of the outer circumferential-side endportion of the lower piece 15 projects downward to form the supportportion 15 a for the side rail 12.

However, in the present embodiment, the portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13are configured as follows. That is, a groove 21 that extends linearly inthe radial direction is formed in the portion on the innercircumferential side from the side rail support portion in each of asurface that is close to the side rail 11 of the upper piece 14 and asurface that is close to the side rail 12 of the lower piece 15 of thespacer expander 13. The grooves 21 are formed by deforming predeterminedportions of the upper piece 14 and the lower piece 15 into an arc shapein section by plasticity processing. Inner circumferential-side endportions of the grooves 21 in the upper piece 14 and the lower piece 15communicate with the through holes 19 in the base portions of the flangeportions 17 and 18, respectively, and outer circumferential-side endportions are open to an external space so as to communicate with theexternal space. Reference numeral 22 denotes the opening. Although thesectional shape of the groove 21 is shown as an arc shape, the presentinvention is not limited thereto, and, for example, an invertedtrapezoidal shape or a V shape may be also used.

As described above, in the combination oil ring 10 according to thepresent embodiment, the side rail support portions 14 a and 15 a of thespacer expander 13 are formed at the center portions in thecircumferential direction of the outer circumferential-side end portionsof the upper piece 14 and the lower piece 15, so that spaces are formedbetween the upper piece 14 of the spacer expander 13 and the upper siderail 11, and between the lower piece 15 of the spacer expander 13 andthe lower side rail 12, at the both side portions 14 b and 15 b of theside rail support portions 14 a and 15 a in the circumferentialdirection of the outer circumferential-side end portions. As a result,oil flows in from the spaces to form a flow of oil from the outercircumferential side to the inner circumferential side, and the oilcontaining sludge is easily discharged from the respective through holes19 in the flange portions 17 and 18 of the spacer expander 13, so thatthe side rails 11 and 12 and the spacer expander 13 can be preventedfrom sticking to each other due to deposits. Moreover, in the presentembodiment, the grooves 21 are formed in the upper piece 14 and thelower piece 15 of the spacer expander 13, so that the sizes of thethrough holes 19 provided at the base portions of the flange portions 17and 18 and facing the space portions between the side rails 11 and 12and the spacer expander 13 can be formed larger by sizes correspondingto the grooves 21 than those of the flat surfaces with no groove;therefore, the deposits between the upper and lower pieces 14 and 15 ofthe spacer expander 13 and the side rails 11 and 12 are easilydischarged from the through holes 19 in the flange portions 17 and 18 ofthe spacer expander 13, and the side rails 11 and 12 and the spacerexpander 13 can be prevented from sticking to each other due to thedeposits. Also, since the grooves 21 extend in the radial direction andare open to the external space so as to communicate with the externalspace without being closed on the outer circumferential side, the oilflows in from the openings 22 to form a flow of oil from the outercircumferential side to the inner circumferential side; therefore, thedeposits become difficult to accumulate and easily discharged from thethrough holes 19 in the flange portions 17 and 18, so that the siderails 11 and 12 and the spacer expander 13 can be further prevented fromsticking to each other due to the deposits.

FIGS. 14 and 15 show yet another embodiment of the present invention.The combination oil ring 10 according to the present embodiment differsfrom the combination oil ring according to the aforementioned embodimentshown in FIG. 7 in the configuration of portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13as described below (also slightly differs in the configuration of theflange portions 17 and 18), and the other configurations are the same asthose in the aforementioned embodiment.

In the present embodiment, a gap between the upper piece 14 of thespacer expander 13 and the side rail 11, and a gap between the lowerpiece 15 and the side rail 12 are continuously widened radially inwardfrom the inner circumferential sides of the side rail support portions14 a and 15 a to the base portions of the flange portions.

That is, in the present embodiment, the upper piece 14 of the spacerexpander 13 has an inclined piece portion 14 c that separates away fromthe side rail 11 radially inward from the inner circumferential side ofthe side rail support portion 14 a to the base portion of the flangeportion 17. Similarly, the lower piece 15 of the spacer expander 13 hasan inclined piece portion 15 c that separates away from the side rail 12radially inward from the inner circumferential side of the side railsupport portion 15 a to the base portion of the flange portion 18.

Each of surfaces that are close to the side rails 11 and 12 of theflange portions 17 and 18 is composed of a lower end surface that standsvertically, and an inclined surface that extends upward therefrom so asto be inclined inward.

The combination oil ring 10 according to the present embodiment furtherprovides following effects in addition to the effects produced by theembodiment shown in FIG. 7. That is, since the gap between the upperpiece 14 and the side rail 11 and the gap between the lower piece 15 andthe side rail 12 of the spacer expander 13, are continuously widenedradially inward from the inner circumferential sides of the side railsupport portions 14 a and 15 a to the base portions of the flangeportions, sticking of the side rails 11 and 12 and the spacer expander13 due to deposits can be suppressed. Also, since the upper piece 14 hasthe inclined piece portion 14 c that separates away from the side rail11 radially inward, oil containing sludge flows on the inclined surfaceof the upper piece 14 to be easily discharged from the through hole 19in the flange portion 17, so that the sticking of the side rail 11 andthe spacer expander 13 due to the deposits can be suppressed.

FIGS. 16 and 17 show yet another embodiment of the present invention.The combination oil ring 10 according to the present embodiment differsfrom the combination oil ring according to the aforementioned embodimentshown in FIG. 7 in the configuration of portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13as described below (also slightly differs in the configuration of theflange portions 17 and 18), and the other configurations are the same asthose in the aforementioned embodiment.

In the present embodiment, a gap between the upper piece 14 and the siderail 11 and a gap between the lower piece 15 and the side rail 12 of thespacer expander 13, are discontinuously widened radially inward from theinner circumferential sides of the side rail support portions 14 a and15 a to the base portions of the flange portions.

In the present embodiment, the upper piece 14 of the spacer expander 13has a stepped piece portion 14 d that separates away from the side rail11 radially inward from the inner circumferential side of the side railsupport portion 14 a to the base portion of the flange portion 17.Similarly, the lower piece 15 of the spacer expander 13 has a steppedpiece portion 15 d that separates away from the side rail 12 radiallyinward from the inner circumferential side of the side rail supportportion 15 a to the base portion of the flange portion 18.

Each of surfaces that are close to the side rails 11 and 12 of theflange portions 17 and 18 is composed of a lower end surface that standsvertically, and an inclined surface that extends upward therefrom so asto be inclined inward.

The combination oil ring 10 according to the present embodiment furtherprovides following effects in addition to the effects produced by theembodiment shown in FIG. 7. That is, since the gap between the upperpiece 14 and the side rail 11, and the gap between the lower piece 15and the side rail 12 of the spacer expander 13, are discontinuouslywidened radially inward from the inner circumferential sides of the siderail support portions 14 a and 15 a to the base portions of the flangeportions, sticking of the side rails 11 and 12 and the spacer expander13 due to deposits can be suppressed. Also, since the upper piece 14 hasthe stepped piece portion 14 d that separates away from the side rail 11radially inward, oil containing sludge flows on the stepped pieceportion 14 d of the upper piece 14 to be easily discharged from thethrough hole 19 in the flange portion 17, so that the sticking of theside rail 11 and the spacer expander 13 due to the deposits can besuppressed.

FIG. 18 shows yet another embodiment of the present invention. Thecombination oil ring 10 according to the present embodiment differs fromthe combination oil ring according to the aforementioned embodimentshown in FIGS. 14 and 15 in the configuration of portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13as described below, and the other configurations are the same as thosein the aforementioned embodiment.

In the present embodiment, a groove 21 that extends linearly in theradial direction is formed in each of the inclined piece portions 14 cand 15 c from the inner circumferential sides side rail support position14 a and 15 a to the base portions of the flange portions in the surfacethat is close to the side rail 11 of the upper piece 14 and the surfacethat is close to the side rail 12 of the lower piece 15 of the spacerexpander 13. The grooves 21 are formed by deforming predeterminedportions of the inclined piece portions 14 c and 15 c of the upper piece14 and the lower piece 15 into an arc shape in section by plasticityprocessing. Inner circumferential-side end portions of the grooves 21 inthe upper piece 14 and the lower piece 15 communicate with the throughholes 19 in the base portions of the flange portions 17 and 18,respectively, and outer circumferential-side end portions are open to anexternal space so as to communicate with the external space. Referencenumeral 22 denotes the opening. Although the sectional shape of thegroove 21 is shown as an arc shape, the present invention is not limitedthereto, and, for example, an inverted trapezoidal shape or a V shapemay be also used.

The combination oil ring 10 according to the present embodiment furtherprovides following effects in addition to the effects produced by theaforementioned embodiment shown in FIGS. 14 and 15. That is, the grooves21 are formed in the upper piece 14 and the lower piece 15 of the spacerexpander 13, so that the sizes of the through holes 19 provided at thebase portions of the flange portions 17 and 18 and facing the spaceportions between the side rails 11 and 12 and the spacer expander 13 canbe formed larger by sizes corresponding to the grooves 21 than those ofthe flat surfaces with no groove; therefore, the deposits between theupper and lower pieces 14 and 15 of the spacer expander 13 and the siderails 11 and 12 are easily discharged from the through holes 19 in theflange portions 17 and 18 of the spacer expander 13, and the sticking ofthe side rails 11 and 12 and the spacer expander 13 due to the depositscan be suppressed. Also, since the grooves 21 extend in the radialdirection and are open to the external space so as to communicate withthe external space without being closed on the outer circumferentialside, the oil flows in from the openings 22 to form a flow of oil fromthe outer circumferential side to the inner circumferential side;therefore, the deposits become difficult to accumulate and easilydischarged from the through holes 19 in the flange portions 17 and 18,so that the sticking of the side rails 11 and 12 and the spacer expander13 due to the deposits can be further suppressed.

FIG. 19 shows yet another embodiment of the present invention. Thecombination oil ring 10 according to the present embodiment differs fromthe combination oil ring according to the aforementioned embodimentshown in FIGS. 16 and 17 in the configuration of portions on the innercircumferential side from the side rail support portions 14 a and 15 aof the upper piece 14 and the lower piece 15 of the spacer expander 13as described below, and the other configurations are the same as thosein the aforementioned embodiment.

In the present embodiment, a groove 21 that extends linearly in theradial direction is formed in each of the stepped piece portions 14 dand 15 d from the inner circumferential sides of the side rail supportportions 14 a and 15 a to the base portions of the flange portions inthe surface that is close to the side rail 11 of the upper piece 14 andthe surface that is close to the side rail 12 of the lower piece 15 ofthe spacer expander 13. The grooves 21 are formed by deformingpredetermined portions of the stepped piece portions 14 d and 15 d ofthe upper piece 14 and the lower piece 15 into an arc shape in sectionby plasticity processing. While inner circumferential-side end portionsof the grooves 21 in the first stepped piece portions 14 d and 15 d ofthe upper piece 14 and the lower piece 15 are open, and outercircumferential-side end portions are open to an external space so as tocommunicate with the external space, inner circumferential-side endportions of the grooves 21 in the second stepped piece portions 14 d and15 d communicate with the through holes 19 in the base portions of theflange portions 17 and 18, respectively, and outer circumferential-sideend portions are open to the external space so as to communicate withthe external space. Reference numeral 22 denotes the respectiveopenings. Although the sectional shape of the groove 21 is shown as anarc shape, the present invention is not limited thereto, and, forexample, an inverted trapezoidal shape or a V shape may be also used.

The combination oil ring 10 according to the present embodiment furtherprovides following effects in addition to the effects produced by theembodiment shown in FIGS. 16 and 17. That is, the grooves 21 are formedin the upper piece 14 and the lower piece 15 of the spacer expander 13,so that the sizes of the through holes 19 provided at the base portionsof the flange portions 17 and 18 and facing the space portions betweenthe side rails 11 and 12 and the spacer expander 13 can be formed largerby sizes corresponding to the grooves 21 than those of the flat surfaceswith no groove; therefore, the deposits between the upper and lowerpieces 14 and 15 of the spacer expander 13 and the side rails 11 and 12are easily discharged from the through holes 19 in the flange portions17 and 18 of the spacer expander 13, and the sticking of the side rails11 and 12 and the spacer expander 13 due to the deposits can besuppressed. Also, since the grooves 21 extend in the radial directionand are open to the external space so as to communicate with theexternal space without being closed on the outer circumferential side,the oil flows in from the openings 22 to form a flow of oil from theouter circumferential side to the inner circumferential side; therefore,the deposits become difficult to accumulate and easily discharged fromthe through holes 19 in the flange portions 17 and 18, so that thesticking of the side rails 11 and 12 and the spacer expander 13 due tothe deposits can be further suppressed.

Although the shape of the side rail support portions 14 a and 15 a isshown as a trapezoidal shape (e.g., see FIG. 20) as viewed from theradial direction in the aforementioned embodiments, the presentinvention is not limited thereto, and the side rail support portions 14a and 15 a may be also formed in, for example, a semi-elliptical shape(e.g., see FIG. 21) or a rectangular shape.

Also, although the side rail support surfaces of the side rail supportportions 14 a and 15 a are formed as flat surfaces in the aforementionedembodiments, the present invention is not limited thereto. A behaviorduring engine operation is stabilized by radially forming the side railsupport surfaces as, for example, tapered surfaces (e.g., see FIG. 22)or arc surfaces (e.g., see FIG. 23), and supporting the side rails 11and 12 at the outer circumferential-side end portions.

Also, as shown in FIG. 24, when a circumferential width of the side railsupport portion 14 a of the upper piece 14 is X and a circumferentialwidth of the upper piece 14 is Y, it is preferable to satisfy therelationship of 0<X/Y≦0.7. The same applies to the lower piece 15.

Also, as shown in FIG. 25, when an axial projecting height of the siderail support portion 14 a of the upper piece 14 is “a” and an axialwidth on the side of the flange portions 17 and 18 of the spacerexpander 13 is “b”, it is preferable to satisfy the relationship of0.02<a/b≦0.2. The same applies to the lower piece 15.

Also, as shown in FIG. 26, when an axial distance from the basepositions of the flange portions 17 and 18 of the spacer expander 13 tothe side rails 11 and 12 is “c” and an axial width of the outercircumferential-side end portion of the spacer expander 13 is “d”, it ispreferable to satisfy the relationship of c≧0.1 mm and c/d=0.04 to 0.3.

If c/d is less than 0.04, the oil containing sludge becomes difficult todischarge from the through holes in the flange portions. If c/d is morethan 0.3, the thickness of the spacer expander around the through holesin the flange portions becomes small.

The spacer expander 13 described above is formed by plasticityprocessing.

1. A combination oil ring comprising a pair of upper and lower siderails and a spacer expander arranged there between, the spacer expanderincluding a plurality of upper pieces and lower pieces alternatelyarranged in a circumferential direction with the pieces axially andcircumferentially apart from each other, a coupling piece coupling anupper piece and a lower piece adjacent to each other, and a flangeportion formed standing at an inner circumferential-side end portion ofeach of the upper pieces and the lower pieces so as to press the siderails, and a through hole being formed in the flange portion, wherein aside rail support portion of the spacer expander is formed at an endportion in the circumferential direction of an outercircumferential-side end portion of each of the upper pieces and thelower pieces: wherein a length of the side rail support portion in thecircumferential direction is shorter than a length of each of the upperpieces and the lower pieces in the circumferential direction so as toform spaces between each of the upper pieces of the spacer expander andthe upper side rail, and between each of the lower pieces of the spacerexpander and the lower side rail, at portions other than side railsupport portions in the circumferential direction of the outercircumferential-side end portions; wherein a length of the side railsupport portion in the radial direction is less than half of that ofupper and lower pieces except flange portions in the radial direction;wherein each of the upper pieces and the lower pieces, other than theside rail support portions, radially extends inward from an outercircumferential-side edge to a base portion of the flange portion in acontinuous flat plane perpendicular to an axial direction; and wherein agroove is formed in the continuous flat plane extending in the radialdirection from the inner circumferential side of the side rail supportportion to the base portion of the flange portion such that an innercircumferential-side end portion of the groove is open to communicatewith the through hole in the flange portion, and an outercircumferential-side end portion of the groove is open to communicatewith an external space.
 2. The combination oil ring according to claim1, wherein the side rail support portion of the spacer expander isformed at an end portion in the circumferential direction of an outercircumferential-side end portion of each of the upper pieces and thelower pieces, and wherein a portion other than the side rail supportportion in the circumferential direction of the outercircumferential-side end portion of each of the upper pieces and thelower pieces of the spacer expander projects to an axially opposite sidefrom the side rail support portion.
 3. The combination oil ringaccording to claim 2, wherein the portion other than the side railsupport portion in the circumferential direction of the outercircumferential-side end portion of each of the upper pieces and thelower pieces of the spacer expander has a radial through hole on aninner circumferential side thereof.